Demodex (class Arachnida, superorder Acariformes) is one of the most commonly found ectoparasites in humans. On the eyelids, D. folliculorum lives in the eyelash follicles and D. brevis lives deep in the meibomian glands and the sebaceous glands of the lashes. They eat skin cells, and oils in the hair follicle. It is reported that Demodex is an etiologic factor in chronic blepharitis, conjunctival inflammation, and meibomian gland dysfunction. Patients who suffer from blepharitis as a result of an ocular Demodex infestation often present a number of symptoms such as foreign body sensation in the eye, redness, and itching. Uncontrolled ocular Demodex infestation in eyelids may cause mal-directed eye lashes (trichiasis), meibomian gland dysfunction leading to lipid tear deficient dry eye, conjunctival inflammation (conjunctivitis), and sight-threatening corneal abnormalities. The symptoms can become severe enough that the patient may require surgery to achieve relief.
Tea tree oil (TTO) is natural oil distilled from the leaf of Melaleuca alternifolia. TTO is known to be effective for killing Demodex in vitro and in vivo. A lid scrubbing treatment with TTO is known to be effective for decreasing Demodex in eyelashes treated with a cotton tip wetted with 10% TTO (Koo et al, J Korean Med Sci 2012; 27: 1574-1579). One of the active components of TTO is terpinen-4-ol. U.S. Pat. No. 8,455,015 discloses that terpinen-4-ol is effective in treating an ocular Demodex infestation or Demodex-induced blepharitis in the form of solutions, suspensions, sprays, lotions, gels, pastes, medicated sticks, balms, cleansers (including shampoos and soaps), creams, or ointments.
Neem oil is a natural oil pressed from the fruits and seeds of the Neem tree (Azadirachta indica). Neem oil is known to be an effective miticide for killing various forms of mites. A component of Neem oil, azadirachtin, works by interfering with the hormone systems of mites to hinder their ability to feed, grow, molt, and reproduce. Once the Demodex mites have been exposed to Neem oil their life cycle is broken and their population will decrease. Although Neem oil is a miticide, it is not known to be useful in the treatment of Demodex blepharitis.